Unlike other commercial silicone hydrogel contact lenses, DAILIES TOTAL1® water gradient silicone hydrogel contact lenses are produced by using an unconventional cast-molding technology—the so-called Lightstream Technology™ (ALCON), as illustrated in U.S. Pat. Nos. 5,508,317, 5,789,464, 5,849,810, 6,800,225, and 8,163,206, which are incorporated by reference in their entireties. The Lightstream Technology™ involves (1) a lens-forming composition, (2) reusable molds produced in high precision, and (3) curing under a spatial limitation of actinic radiation (e.g., UV/Visible light) for a very short period of time (e.g., less than about 30 seconds). Lenses produced according to the Lightstream Technology™ can have high consistency and high fidelity to the original lens design, because of use of reusable, high precision molds. In addition, contact lenses with high quality can be produced at relatively lower cost due to the short curing time and a high production yield. However, the Lightstream Technology™ has not been applied to make UV-absorbing silicone hydrogel contact lenses.
Furthermore, due to the presence of UV-absorber and possibly some visibility-tinting agents, the photocuring of a lens-forming composition in a mold may not be effected uniformly and resultant lenses may have unacceptable internal stress derived from the non-uniform curing.
Therefore, there is still a need for a method for making UV-absorbing silicone hydrogel contact lenses having no or minimal internal stress, according to a photocuring technology, especially according to the Lightstream Technology™.